Conventionally, there is known a stator comprising a plurality of divided cores annularly arranged and constituting a stator core, and an annular holder disposed outside the plurality of divided cores and integrally holding the plurality of divided cores (for example, refer to Patent Literature 1).
In the stator of Patent Literature 1, the divided cores and the holder have recess parts and projection parts extending parallel to the center axis line of the stator, respectively. Further, when the divided cores and the holder are integrated together to form the stator, the holder is attached onto the divided cores by loosely fitting the projection parts into the recess parts, and then, the projection parts are deformed by punching. Thus, since the gaps between the recess parts and the projection parts are filled, which further generates residual stress, the stator in which the divided cores and the holder are firmly fasten is formed.
The stator of another aspect of Patent Literature 1 is formed by fitting a cylindrical holder onto the outer periphery of the annular arrangement in which the plurality of divided cores are annularly arranged, and pressing the holder from the outer circumferential surface toward the inner circumferential surface with a punch for plastic deformation or the like. In this case, pressing with the punch or the like causes the material of the holder to enter the grooves of the divided cores and the like, and the divided cores and the holder to be integrated together.
Such a stator has sufficient connection strength between the divided cores and the holder in the case where it is used for a small motor such as a driving motor for hard disks. Nevertheless, since, in the case where large torque is given thereto as in a driving motor for vehicles or the like, fixing strength of the divided cores with respect to the holder is not sufficient, there is a concern that the divided cores are disassembled from the holder.
Therefore, typically in the case of a stator used for a driving motor of vehicles, the stator is formed by press-fitting or shrink-fitting the holder onto the outer circumferential surface of the annular arrangement of the divided cores, and fastening the annular arrangement with the holder under strong force. Thus, since sufficient fixing strength of the divided cores with respect to the holder can be obtained, the stator core can be prevented from getting out of the holder under large torque.